Multiple gaseous discharge display/memory panel having thin film dielectric charge storage member

ABSTRACT

There is disclosed a multiple gaseous discharge display/memory panel having an electrical memory and capable of producing a visual display, the panel being characterized by an ionizable gaseous medium in a gas chamber formed by a pair of opposed charge storage members which are respectively backed by a series of parallel-like conductor (electrode) members, the conductor members behind each charge storage member being transversely oriented with respect to the conductor members behind the opposing charge storage member so as to define a plurality of discrete discharge volumes constituting a discharge unit, each charge storage member being comprised of a continuous thin film of dielectric material having a thickness of 150,000 angstrom units or less.

United States Patent 1191 Hoehn et a1.

[ 1 Dec. 3, 19 74 1 MULTIPLE GASEOUS DISCHARGE DISPLAY/MEMORY PANELHAVING THIN FILM DIELECTRIC CHARGE STORAGE MEMBER [75] Inventors: HaroldJ. Hoehn, Toledo; Roger E.

Ernsthausen, Luckey, both of Ohio [73] Assignee: Owens-Illinois, Inc.,Toledo, Ohio [22] Filed: Sept. 21, 1973 [21] Appl. No.: 399,548

[52] U.S. Cl 313/201, 313/220, 313/221, 315/169 TV [51] Int. Cl H01j61/30, H0lj 65/04 [58] Field of Search 313/201, 220, 221; 1 315/169 TV[56] References Cited UNITED STATES PATENTS 2,960,617, 11/1960 Lodge eta1 .j. 313/65 x 3,189,781 6/1965 Lcmpert 313/68 R X 3,377,498 4/1968Koury ct al. 1 .1 313/221 3,440,477 4/1969 Crowell et a1. 1 313/66 X3,614,509 10/1971 Willson 313/201 3,624,444 11/1971 Berthold et a1.313/221 3,634,719 l/l972 Ernsthausen 313/221 OTHER PUBLICATIONS GasDisplay Panel," B. Welber, IBM Technical Disclosure Bulletin, Vol. 12,No. 10, March 1970. pp. 1552-1553.

Primary E,\'aminerHerman Karl Saalbach Assistant Examiner-Eugene R.LaRoche Attorney, Agent, or Firm-Donald Keith Wedding [57] ABSTRACTThere is disclosed a multiple gaseous discharge display/memory panelhaving an electrical memory and capable of producing a visual display,the panel being characterized by an ionizable gaseous medium in a gaschamber formed by a pair of opposed charge storage members which arerespectively backed by a series of parallel-like conductor (electrode)members, the con ductor members behindeach charge storage member beingtransversely oriented with respect to the conductor members behind theopposing charge storage member so as to define a plurality of discretedischarge volumes constituting a discharge unit, each charge storagemember being comprised of a continuous thin film of dielectric materialhaving a thickness of 150,000 angstrom units or less.

3 Claims, 7 Drawing Figures I PATENIELUEB 3 914 3,852,607

' sum 10; a

MULTIPLE GASEOUS DISCHARGE DISPLAY/MEMORY PANEL HAVING THIN FILMDIELECTRIC CHARGE STORAGE MEMBER RELATED APPLICATION This is acontinuation-in-part of copending U.S. Pat. Application Ser. No.146,796, filed May 25, 1971, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to novel multiple gasdischarge display/memory panels which have an electrical memory andwhich are capable of producing a visual display or representation ofdata such as numerals, letters, television display, radar displays,binary words, etc.

Multiple gas discharge display and/or memory panels of one particulartype with which the present invention is concerned are characterized byan ionizable gaseous medium, usually a mixture of at least two gases atan appropriate gas pressure, in a thin gas chamber or space between apair of opposed dielectric charge storage members which are backed byconductor (electrode) members, the conductor members backing eachdielectric member typically being appropriately oriented so as to definea plurality of discrete gas discharge units or cells.

In some priorart panels the discharge cells are additionally defined bysurrounding or confining physical structure such as apertures inperforated glass plates and the like so as to be physically isolatedrelative to other cells. In either case, with or without the confiningphysical structure, charges (electrons, ions) produced upon ionizationof the elemental gas volume of a selected discharge cell, when properalternating operating potentials are applied to selected conductorsthereof, are collected upon the surfaces of the dielectric atspecifically defined locations and constitute an electrical fieldopposing the electrical field which created them so as to terminate thedischarge for the remainder of the half cycle and aid in the initiationof a discharge on a succeeding opposite half cycle of applied voltage,such charges as are stored consituting an electrical memory.

Thus, the dielectric layers prevent the passage of substantialconductive current from the conductor members to the, gaseous medium andalso serve as collecting surfaces for ionized gaseous medium charges(electrons, ions) during the alternate half cycles of the A.C.,operating potentials, such charges collecting first on one elemental ordiscrete dielectric surface area and then 'on an opposing elemental ordiscrete dielectric surface area on alternate half cycles to consitutean electrical memory.

An example of a panel structure containing nonphysically isolatedor'open dischargecells is disclosed in U.S. Pat.'No. 3,499,l67issued toTheodore C. Baker, et al.

An exampleof a panel containing physically isolated cells is disclosedin the article by D. L. Bitzer and H. G. Slottow entitled The PlasmaDisplay Panel A Digitally Addressable Display With Inherent Memory,"Proceeding. of the- Fall Joint Computer Conference IEEE, San Francisco,Calif, Nov. 1966, pages 541-547. Also reference is made to U.S. Pat. No.3,559,190. I

In the construction of the panel, a continuous volume of ionizable gasis confined between a pair of dielectric surfaces backed by conductorarrays typically forming matrix elements. The cross conductor arrays maybe orthogonally related (but any other configuration of conductor arraysmay be used) to define aplurality of opposed pairsof charge storageareas on the surfaces of the dielectric boudning or confining the gas.Thus, for a conductor matrix having H rows and C columns the number ofelemental or discrete areas will be twice the number of suchelemental'discharge cells. In addition, the panel may comprise aso-called monolithic structure in which the conductor arrays are createdon a single substrate and wherein two or more arrays are separated fromeach other and from the gaseous medium by at'least one insulatingmember. In such a device the gas discharge takes place not between twoopposing electrodes, but between two contiguous or adjacent electrodeson the same substrate; the gas being confined between the substrate andan outer retaining wall. 7

It is also feasible to have a gas discharge device wherein some of theconductive or electrode members are in direct contact with the gaseousmedium and the remaining electrode members are appropriately insulatedfrom such gas, i.e., at least one insulated electrode.

In addition to the matrix configuration, the conduc tor arrays may beshaped otherwise. Accordingly, while the preferred conductor arrangementis of the crossed grid type as discussed herein, it is likewise apparentthat where a maximal variety of two dimensional display patterns is notnecessary, as where specific standardized visual shapes '(.e.g.,numerals, letters, words, etc.) are to be formed and image resolution isnot critical, the conductors may be shaped accordingly, i.e., asegmented display.

The gas is one which produces visible light or invisible radiation whichstimulates a phosphor (if visual display is an objective) and a copioussupply of charges (ions and electrons) during discharge.

In the prior art, a wide variety of gases and gas mixtures have beenutilized as the gaseous medium in a numberof different gas dischargedevices; Typical of such gases include pure gases and mixtures of C0; C0halogens; nitrogen; NH oxygen, water vapor; hydrogen; hydrocarbons; P Oboron fluoride, acid fumes; TiCl air; H 0 vapors of sodium, mercury,thallium, cadmium, rubidium, and cesium; carbon disulfide, laughing gas;H 8; deoxygenated air; phosphorous vapors; C H CH naphthalene vapor;anthracene; freon, ethyl alcohol; methylene bromide; heavy hydrogen;electron attaching gases; sulfur hexafluoride; tritium; radioactivegases; and the so-called rare or inert Group VIII gases.

In an open cell Baker, et'al., type panel, the gas pressure and theelectric field are sufficient to laterally confine charges generated ondischarge within elemental or discrete dielectric areas within theperimeter of such areas, especially in-a panel containing non-isolateddischarge cells. As described "in the Baker, et al., patent, the spacebetween the dielectric surfaces occupied by the gas is such as to permitphotons generated on discharge in a selected discrete or elementalvolume of gas to pass freely through the gas space and strike surfaceareas of dielectric remote from the. selected discrete volumes,suchremote, photon struck dielectric surface areas thereby emittingelectrons so as to condition at least one elemental volume other thanthe elemental volume in which the photons originated.

With respect to the memory function of a given discharge panel, theallowable distance or spacing be tween the dielectric surfaces depends,inter alia, on the frequency of the alternating current supply, thedistance typically being greater for lower frequencies.

, While the prior art does disclosed gaseous discharge devices havingexternally positioned electrodes for initiating a gaseous discharge,sometimes called electrodeless discharge, such prior art devicesutilized frequencies and spacing or discharge volumes and operatingpressures such that although discharges are initiated in the gaseousmedium, such discharges are ineffective or not utilized for chargegeneration and storage at higher frequencies; although charge storagemay be realized 'at lower frequencies, such charge storage has not beenutilized in a display/memory device in the manner of the Bitzer-Slottowor Baker, et al., invention. The term memory margin is defined herein aswhere V, is the half amplitude of the smallest sustaining voltage signalwhich results in'a discharge every half cycle, but at which the cell isnot bi-stable and V -is the half amplitude of the minimum appliedvoltage sufficient to sustain discharges once initiated.

It will be understood that the basic electrical phenomenon utilized inthis invention is the generation of charges (ions and electrons)alternately storable at pairs of opposed or facing discrete points orareas on a pair of dielectric surfaces backed by conductors connected toa source of operating potential. Such stored charges resultin anelectrical field opposing the field produced by the applied potentialthat created them and hence operate to terminate ionization in theelemental gas volume between opposed or facing discrete points or areasof dielectric surface. The term sustain a discharge means producing asequence ofmomentary discharges, at least onedischarge for each halfcycle of applied alternating sustaining voltage, once the elemental gasvolume has been fired, to maintain alternate storing of charges at pairsof opposed discrete areas on the dielectric surfaces.

As used herein, a cell is in the on state when a quantity of charge isstored in the cell such that on each half cycle of the sustainingvoltage, a gaseous discharge is produced. t

In addition to the sustaining voltage,other voltages may be utilized tooperate thepanel, such as firing, ad-

dressing, and writing voltages.

A firing voltage is any voltage, regardless of source, required todischarge a cell. Such voltage may be completely external in origin ormay be comprised of internal cell wall voltage in combination withexternall'y originated voltages.

An addressing voltage is a voltage produced on the panel X Y electrodecoordinates such that at the selected cell or cells, the total voltageapplied across the cell is equal to or' greater than the firing voltagewhereby the cell'is discharged.

A fwriting'voltage is an addressing voltage of sufficient magnitude tomake it probable that on subsequentsustaining voltage half cycles, thecell will be in the on state. T

In the operation of a multiple gaseous discharge device, of the typedescribed hereinbefore, it is necessary to condition the discreteelemental gas volume of each discharge cell by supplying at least onefree electron thereto such that a gaseous discharge can be initiatedwhen the cell is addressed with an appropriate voltage signal.

The prior art has disclosed and practiced various means for conditioninggaseous discharge cells.

One such means of panel conditioning comprises a socalled electronicprocess whereby an electronic con- I ditioning signal or pulse isperiodically applied to all of the panel discharge cells, as disclosedfor example in British patent specification No. 1,161,832, page 8, lines56 to 76. Reference is also made to US. Pat. No. 3,559,190 and TheDevice Characteristics of the Plasma Display Element" by .Iohnson,'etal., IEEE Transactions On Electron Devices, September, 1971. However,electronic conditioning is self-conditioning and is only effective aftera discharge cell has been previously conditioned; that is, electronicconditioning involves periodically discharging a cell and is therefore away of maintaining the presence of free electrons. Accordingly, onecannot wait too long between the periodically applied conditioningpulses since there must be at least one free electron present in orderto discharge and condition a cell. 7

Another conditioning method comprises the use of external radiation,such as flooding part or all of the gaseous medium of the panel withultraviolet radiation. This external conditioning method has the obviousdisadvantage that it is not always convenient or possible to provideexternal radiation to a panel, especially if the panel is in a remoteposition. Likewise, an external UV source requires auxiliary equipment.Accordingly, the use of internal conditioning is generally preferred.

One internal conditioning means comprises using internal radiation, suchas by the inclusion of'a radioactive material. J i

Another means of internal conditioning, which we call photonconditioning, comprises using one or more so-called pilot dischargecells in the on-state for the generation of photonsyThis is particularlyeffective in a so-called open cell construction (as described in theBaker, et al., patent) wherein the space between the dielectric surfacesoccupied by the gas is such as to permit photons generated on dischargein a selected discrete orelemental volume of gas (discharge cell) topass freely through the panel gas space so as to condition other andmore remote elemental volumes of other discharge units. In addition toor in lieu of the pilot cells, one may use other sources of photonsinternal to the panel.

Internal photon conditioning may be unreliable when a given dischargeunit to be addressed is remote in dis-' tance relative to theconditioning source, e.g., the pilot cell. Accordingly, a multiplicityof pilot cells may be required for the conditioning of a panel having alarge geometric area. In one highly convenient arrangement, thepanel'matrix border (perimeter) is comprised of a plurality of suchpilot cells.

DRAWINGS ILLUSTRATING GAS DISCHARGE ,DISPLAY/MEMORY PANEL Reference ismade to the accompanying drawings and the hereinafter discussed FIGS. 1to 4 shown thereon illustrating a gas discharge display/memory panel ofthe Baker, et al. type.

FIG. 1 is a partially cut-away planview of a gaseous dischargedisplay/memory panel as connected to a diagrammatically illustratedsource of operating potentials. FIG. 2 is a cross-sectional view(enlarged, but not to proportional scale since the thickness of the gasvolume, dielectric members and conductor arrays have been enlarged forpurposes of illustration) taken on lines 2 2 of FIG. 1.

FIG. 3 is an explanatory partial cross-sectional view similar to FIG. 2(enlarged, but not to proportional scale).

FIG. 4 is an isometric view of a gaseous discharge display/memory panel.

FIGS. 5, 6, and 7 are partial cross-sectional views illustrating threedifferent embodiments of this inventron.

The invention utilizes a pair of dielectric films 10 and 11 separated bya thin layer or volume of a gaseous dis charge medium 12, the medium 12producing a copious supply of charges (ions and electrons) which arealternately collectable on the surfaces of the dielectric members atopposed or facing elemental or discrete areas X and Y defined by theconductor matrix on nongas-contacting sides of the dielectric members,each dielectric member presenting large open surface areas and aplurality of pairs of elemental X and Y areas. While the electricallyoperative.structural members such as the dielectric members 10 and 11and'conductor matrixes 13 and 14 are all relatively thin (beingexaggerated in thickness i n the drawings) they are formed on andsupported by rigid nonconductive support members 16 and 17 respectively.I

Preferably one or both of nonconductive support members 16 and 17 passlight produced by discharge in the elemental gas volumes. Preferably,they are transparent glass members and thesemembers essentially definethe overall thickness and strength of the panel. Forexample, thethickness of gas layer 12 as determined by spacer 15 is usually under 10mils and preferably about 4 to 8 mils, dielectriclayers l0 and 11 (overthe conductors at the elemental or discrete X and Y areas) are usuallybetween 1 and 2 mils thick, and conductors 13 and .14 about 8,000angstroms thick. However, support members 16 and 17 are much thicker(particularly in larger panels) so as to provide as much ruggednessasmay be desired to compensate for stresses in the panel. Support members16 and 17 also serve as heatsinks for heat generated by discharges andthus minimize the effect of temperature on operation of .the device. Ifit is desired that only the mem'ory'function be utilized, then none ofthe members need by transparent to light.

Except for being nonconductive or good insulators the electricalproperties of support members 16 and 17 are not critical. The mainfunction of support members 16 and 17 is to provide mechanical supportand strength for the entire panel, particularly with respect to pressuredifferential acting on the paneland thermal shock. As noted earlier,they should have-thermal expansion characteristics substantiallymatching the thermal expansion characteristics of dielectric layers 10and 11. Ordinary 1/4 inch commercial grade soda lime plate glasses havebeen used for thispurpose. Other glasses such as low expansion glassesor transparent devitrified glasses can be used provided they canwithstand processing and have expansion characteristics substantiallymatching expansion characteristics of the dielectric coatings 10 and 11.For given pressure differentials and thickness of plates, the stress anddeflection of plates may be determined by following standard stress andstrain formulas (see R. J. Roark, Formulas for Stress and Strain,McGraw-Hill, 1954).

Spacer 15 may be made of the same glass material as dielectric filmsland 11 and may be an integral rib formed on one of the dielectricmembers and fused to the other members to form a bakeable hermetic sealenclosing and confining the ionizable gas volume 12. However, a separatefinal hermetic seal may be effected by a high strength devitrified glasssealant 15S. Tubulation 18 is provided for exhausting the space betweendielectric members 10 and 11 and filling that space with the volume ofionizable gas. For large panels small beadlike solder glass spacers suchas shown at 15B may be located between conductor intersections and fusedto dielectric members 10 and 11 to aid in withstanding stress on thepanel and maintain uniformity of thickness of gas volume 12.

Conductor arrays 13 and 14 may be formed onsupport members 16 and 17 bya number of well-known processes, such. as photoetching, vacuumdeposition, stencil screening, etc. In the panel shown in FIG. 4, thecenter-to-center spacing of conductors in the respective arrays is about17 mils. Transparent or semitransparent conductive material such as tinoxide, gold, or aluminum can be used toform the conductor arrays andshould have a resistance'less than 3,000 ohms per line. Narrow opaqueelectrodes may alternately be used so that discharge light passes aroundthe edges of the electrodes to the viewer. It is important to-select aconductor material thatis not attacked during processing by thedielectric material.

It will be appreciated that conductor arrays 13 and 14 may be wires orfilaments of copper, gold, silver or aluminum or any other conductivemetal or material. For example 1 mil wire filaments are commerciallyavailable and may be used in the invention. However, formed in situconductor. arrays are preferred since they may be more easily anduniformly placed on and adhered to the support plates 16 and 17,

Dielectric layer members 10 and 11 are formed of an inorganic materialand are preferably formed in situ as an adherent film or coating whichis not chemically or physically affected during bake-out of the panel.One such material is a solder glass such as Kimble SG-68 manufactured byand commercially available from the assignee of the present invention.

This glass has thermal expansion characteristics substantially matchingthe thermal expansion characteristics of certain soda-lime glasses, andcan be'used as the dielectric layer when the support members 16 and 17are soda-lime glass plates. Dielectric layers 10 and 11 must be smoothand have a dielectric breakdown voltage of about 1,000 v. andbeelectrically homogeneous on a microscopic scale (e.g., no cracks,bubbles, crystals, dirt, surface films, etc.). In addition, the surfacesof dielectric layers 10 and 11 should be good photoemitters of electronsin a baked out condition. Alternately, dielectric layers 10 and 11 maybe overcoated with materials designed to produce good electron emission,as in US. PatrNo. 3,634,719, issued to Roger E.

Ernsthausen. Of course, for an optical display at least one ofdielectric layers 10 and 11 should pass light generated on discharge andbe transparent or translucent and, preferably, both layers are opticallytransparent.

The preferred spacing between surfaces of the dielectric films is about4 to 8 mils with conductor arrays 13 and 14 having center-to-centerspacing of about 17 mils.

The ends of conductors 14-1 14-4 and support member 17 extend beyond theenclosed gas volume 12 and are exposed for the purpose of makingelectrical connection to interface and addressing circuitry 19.Likewise, the ends of conductors 13-1 13-4 on support member 16 extendbeyond the enclosed gas volume 12 and are exposed for the purpose ofmaking electrical connection to interface and addressing circuitry 19. I

As in known display systems, the interface and addressing circuitry orsystem 19 may be relatively inexpensive line scan systems or thesomewhat more expensive high speed random access systems. in eithercase, it is to be noted that a lower amplitude of operating pobeeninitiated by application to conductor 13-1 and conductor 14-1 firingpotential V, as derived from a source 35 of variable phase, for example,and source 36 of sustaining potential V, (which may be a sine wave, forexample). The potential V, is added to the sustaining potential V, assustaining potential V increases in magnitude to initiate theconditioning discharge about the center of elemental volume 30 shown inHO. 3. There, the phase of the source 35 of potential V, has beenadjusted into adding relation to the alternating voltage from the source36 of sustaining voltage V to provide a voltage V,', when switch 33 hasbeen closed,

'to conductors 13-1 and 14-1 defining elementary gas volume 30sufficient (in time and/or magnitude) to produce a light generatingdischarge centered about discrete elemental volume 30. At the instantshown, since conductor 13-1 is positive, electrons 32 have coilected onand are moving to an elemental area of dielectric member substantiallycorresponding the tentials helps to reduce problems associated with theinterface circuitry between the addressing system and thedisplay/mernorypanel, per se. Thus, by providing a panel having greater uniformity inthe discharge characteristics throughout the panel, tolerances andoperating characteristics of thepanel with which the interfacingcircuitry cooperate, are made less rigid.

One mode of initiating operation of the panel will be described withreference to FIG. 3, which illustrates the condition of one elementalgas volume 30 having an e]- emental cross-sectional area and volumewhich is quite small relativeto the entire volume and cross-sectionalarea of gas 12. The cross-sectional area of volume 30 is defined bytheoverlapping common elemental areas of the conductor arrays and thevolume is equal to the product of the distance between the dielectricsurfaces and the elemental area. it is apparent that if the conductorarrays are uniform and linear and are orthogonally (at right angles toeach other) related each of elemental areas-X and Y will be squaresandif conductors of one conductor array are wider than conductors of theother conductor arrays, said areas will be rectangles. if theconductorarrays are at transverse angles relative to each other, otherthan. 90, the areas will be diamond shaped so that thecross-sectionalshape of each volume is determined solely in the first instance bytheshape of the common area of overlap between conductors in theconductor arrays 13 and 14. The dotted lines 30' are imaginary lines toshow a boundary of one elemental volume about the center of which eachelemental discharge takes place. As described earlier herein, it isknown that the cross-sectional area of the dischargein a gas is affectedby, inter alia, the pressure of the gas, such that, if desired, thedischarge may even be constricted to within an area smaller than thearea of conductor overlap. By utilization of this phenomena, the lightproduction may be confined or resolved substantially to the area of theelemental cross-sectional area defined by conductor overlap. Moreover,by operating at such pressure charges (ions and electrons) produced ondischarge are laterally confined so as to not materially affectoperation of adjacent elemental dis-. charge volumes. I

In the instant shown in FIG. 3, a conditioning discharge about thecenter of elemental volume 30 has area of elemental gas volume 30 andthe less mobile positive ions 31 are beginning to collect on the opposedelemental area of dielectric member 11 since it is negative. As thesecharges build up, they constitute a back voltage opposed to the voltageapplied to conductors I 13-1'and 14-1 and serve to terminate thedischarge in elemental gas volume 30 for the remainder of a half cycle.

During the discharge about the center of elemental gas volume 30,photons are produced which are free to move or pass through gas medium12, as indicated by arrows 37, to strike or impact remote surface areasof photoemissive dielectric members 10 and 11, causing such remote areasto release electrons 38. Electrons 38 are, in effect, free electrons ingas medium 12 and condition each other discrete elemental gas volume.for operation at a lower firing potential V; which is lower in magnitudethan thefiring potential V, for the initial discharge about the centerof elemental volume 30 and this voltage is substantially uniform foreach other elemental gas volume.

Thus, elimination of physical obstructions or barriers between discreteelemental volumes, permits photons to travel via the space occupied bythe gas medium 12 to impact remote surface areas of dielectric members10 and 11 and provides a mechanism for supplying free electrons to allelemental gas volumes, thereby conditioning all discretev elemental gasvolumes for subsequent discharges, respectively, at a uniform lowerapplied potential. While in FIG. 3 a single elemental volume 30 isshown, it will be appreciated that an entire row (or column) ofelemental gas volumes may be maintained in a tired condition duringnormal ope ration of the device with the light produced thereby beingmasked or blocked off from the normal viewing area and not used fordisplay purposes. It can be expected that in some applications therewill always be at least oneelemental volume in a tired condition andproducing light in a panel, and in such applications it is not necessaryto provide separate discharge or generation of photons for purposesdescribed earlier.

However, as described earlier, the entire gas volume can be conditionedfor operation at uniform tiring potentials by use of external orinternal radiation so that there will be no need for a separate sourceof higher potential for initiating an initial discharge. Thus, byradiating the panel with ultraviolet radiation orby inclusion of aradioactive material within the glass materials or gas space, alldischarge volumes can be operated at uniform potentials from addressingand interface circuit 19.

Since each discharge is terminated upon a build up or storage of chargesat opposed pairs'of elemental areas, the light produced is likewiseterminated. In fact, light production lasts for only a small fraction ofa half cycle of applied alternating potential and depending on designparameters, is in the nanosecond range.

After the initial firing or discharge of discrete elemental gas volume30 by a firing potential V switch 33 may be opened so that only thesustaining voltage V, from source 36 is applied to conductors 13-1 and14-1. Due to the storage of charges (e.g., the memory) at the opposedelemental areas X and Y, the elemental gas volume 30 will dischargeagain at or near the peak of negative half cycles of sustaining voltageV to again produce a momentary pulse of light. At this time, due toreversal of field direction, electrons 32 will collect on and be storedon elemental surface area Y of dielectric member 11 and positive ions 31will collect and be stored on elemental surface area X of dielectricmember 10..After a few cycles of sustaining voltage V,, the times ofdischarges become symmetrically located with respect to the wave form ofsustaining voltage V,. At

remote elemental volumes, as for example, the elemental volumes definedby conductor 14-1 with conductors 13-2 and 13-3, a uniform magnitude orpotential V, from source 60 is selectively added by one or both ofswitches 34-2 or 34-3 to the sustaining voltage V,,

shown as 36, to fire one or both of these elemental discharge volumes.Due'to the presence of free electrons produced as a result of thedischarge centered about elemental volume 30, each of these remotediscrete elemental volumes have been conditioned for operation atuniform firing potential V,.

In order to turn of an elemental gas volume (i.e., terminate a sequenceof discharge representing the on state), the sustaining voltage may beremoved. However, since this would also turn off other elemental volumesalong a row or column, it is preferred that the volumes be selectivelyturned off by application to selected on elemental volumes a voltagewhich can neutralize the charges stored at the pairs of opposedelemental areas. This can be accomplished in a number of ways, as forexample, varying the phase or time position of the potential from source60 to where the voltage combined with the potential from source 36'falls substantially below the sustaining voltage.

It is apparent that the plates 16-17 need not be flat but may be curved,curvature of facing surfaces of each plate being complementary to eachother. While the preferred conductor arrangement is of the crossed gridtype as shown herein, it is likewise apparent that where an infinitevariety of two dimensional display patterns are not necessary, as wherespecific standardized visual shapes (e.g., numerals, letters, words,etc.) are to be formed and image resolution is not critical, theconductors may be shaped accordingly. Reference is made to British Pat.Specification 1,302,148 and U .S. Pat. No. 3,71 1,733 wherein non-gridelectrode arrangements are illustrated.

The device shown in FIG. 4 is a panel having a large number of elementalvolumes similar to elemental volume (FIG. 3). In this case more room isprovided to make electrical connection to the conductor arrays 13' and14, respectively, by extending the surfaces of support members 16' and17 beyond seal 15S, alternate conductors being extended on alternatesides Conductor arrays 13 and 14' as well as support members 16 and 17are transparent. The dielectric coatings are not shown in FIG. 4 but arelikewise transparent so that the panel may be viewed from either side.

THE INVENTION In accordance with the practice of this invention, thereis provided a gaseous discharge display/memory device having chargestorage members, each of which comprises at least one thin continuousdielectric film having a minimum thickness sufficient to store chargeswithout breaking down or otherwise deteriorating upon gas discharge dueto thermal, physical, electrical, or other operation originated stressesand having a maximum thickness less than that thickness where the filmbecomes discontinuous due to breakdown caused by deposition originatedstresses.

In the practice hereof, it is contemplated that the dielectric thicknessmay typically range from about 250 angstrom units up to about 150,000angstrom units, preferably about 10,000 angstrom units up to about100,000 angstrom units.

Thethin dielectric film may comprise a single layer or a combination oftwo or more layers, each layer being of the same or differentcomposition.

In the broad practice hereof, it is contemplated using a thin dielectricfilm comprised of one or'more layers selected from any suitable metal ormetalloid compound, particularly oxides. 1

It is especially contemplated using oxides of Al, Ti, Zr, Hf, Si, Pb, orGroupa [IA (Be, Mg, Ca, Sr, Ba, or Ra).

One specific combination contemplated herein comprises a first layerofsilicon oxide having a thickness of about 10,000 angstrom units toabout 70,000 angstrom units, a second layer of aluminum oxide having athickness of about angstrom units to about 2,000 angstrom units, and athird (or top) layer of lead oxide having a thickness of about 100angstrom units to about 2,000 angstrom units.

Another specific combination includes a first layer of I about 10,000angstrom units to about 70,000 angstrom units of silicon oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof lead oxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 70,000 angstrom units of silicon oxide and about100 angstrom units to about 2,000 angstrom unitsof magnesium oxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 70,000 angstrom units of silicon oxide, about100 angstrom units to about 2,000 angstrom units of aluminum oxide, andabout 100 angstrom units to about 2,000 angstrom units of magnesiumoxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 125,000 angstrom units of aluminum oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof lead oxide.

Another specific combination includes a first layer of about 10,000angstrom' units to about 125,000 angstrom units of aluminum oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof magnesium oxide.

Another specific combination includes a first layer of about l0,000angstrom units to about 40,000 angstrom units of magnesium oxide, about40,000 angstrom units to about 90,000 angstrom units of aluminum oxide,and about I angstrom units to about 2,000 angstrom units of lead oxide.

In addition, one or more dielectric layers may be of an electronemissive substance, as discussed in copending U.S. Pat. Application Ser.No. 67,604, filed Aug. 27, i970, and owned by the same assignee of theinstant application.

It may be especially useful to use an electron emissive substance as thetop layer in the dielectric, e.g., with a thicknessof about 100 angstromunits to about 2,000

angstrom'units. Typical electron emissive materials include not by wayof limitation Group IA elements, Group IA oxides, GaAs, GaP, lnAs, InSb,lnP, NiO, CsF, Csl, AgOCs, and AuOCs. Use of CS1 has resulted insubstantially lower operating voltages in a gas discharge device.

As used herein the terms film or layer are intended to be all inclusiveof other similar terms such as deposit, coating, finish, spread,covering, etc.

It is contemplated that each'dielectric oxide layer may be applieddirectly to the supporting substrate or formed in situ thereon.

Typical means of applying a dielectric layer directly to a supportingsubstrate include not by way of limitation vapor deposition; vacuumdeposition; chemical .vapor deposition; wet spraying upon the surface amixture or solution of the dielectric composition suspended or dissolvedin a liquid followed by evaporation of the liquid; dry spraying of thedielectric composition; electron beam evaporation; plasma flame and/orare spraying and/or deposition; ion plating; and sputtering targettechniques. Likewise, combinations of such techniques may be used. l Insitu processes include applying a metal or metaloid (or source thereof)to the supporting substrate and then oxidizing the applied material; Theapplying of the metal, metalloid, or source thereof may be by anyconvenient means, such as discussed hereinbefore vapor deposition;vacuum deposition, etc.

One specific in situ process comprises applying metal or metalloid meltfollowed by oxidation of the melt during the cooling thereof soas toform the oxide layer. Another in situ process comprises an oxidizablesource of the elemental metal or metalloid to the surface. Typical ofsuch oxidizable sources include minerals and/or tures has the furtheradvantage of reducing the number of electrode breaks and substratewarping.

Although this invention has been primarily described hereinbefore withreference to thin dielectric oxide compositions, other metal.or-metalloid compounds may be utilized, especially the halides such. asMgF BeF CaF ,'NaCl, etc. Likewise, glass or ceramic compositions may beutilized, especially the dolomitic aluminosilicates, borosilicates, leadsilicates, and lead borosilicates In FIG. 5, there is shown substrates16, 17, gaseous medium I2, electrodes 13, 14, and thin dielectric layers100, 110.

In FIG. 6, there is shown substrates 16, 17, gaseous medium 12,electrodes 13, 14, thin dielectric layers 200, 210, and dielectricovercoats 201, 211.

In FIG. 7, there is shown substrates 16, 17, gaseous medium 12,electrodes 13, 14, thin dielectric layers 300, 310, first overcoats 301,311, and second overcoats 302, 312.

We claim:

1. In a gaseous discharge display/memory device comprising an ionizablegaseous medium in a sealed gas chamber formed by a pair of opposedcharge storage members backed by electrode members, the improvementwherein at least one charge storage member, consisting of at least twothin continuous dielectric layers, has an effective thickness rangingbetween about 250 angstrom units and about 150,000 angstrom units, theminimum thickness being sufficient to store charges withoutdeteriorating upon gas discharge and the maximum thickness being lessthan that thickness at which said charge storage member becomesdiscontinuous due to breakdown caused by deposition originated stresses,said charge storage member having a first layer of silicon oxide and atleast one additional layer selected from the oxides of Al, Ti, Zr, Hf,Pb, and Group IIA.

2. In a gaseous discharge display/memory device comprising an ionizablegaseous medium in a sealed gas chamber formed by a pair of opposedcharge storage members backed by electrode members, the improvementwherein at least one charge storage member, comprising a plurality oflayers, has an effective thickness ranging between about 250 angstromunits and about 150,000 angstrom units, the minimum thickness beingsufficient to store charges without deteriorating upon gas discharge andthe maximum thickness being less than that thickness at which saidcharge storage member becomes discontinuous due to breakdown caused bydeposition originated stresses, the top layer of said charge storagemember'comprising an electron emissive material selected from GroupIAelements, Group IA oxides, GaAs, GaP, lnAs, InSb, InP, NiO, CsF, Csl,AgOCs and AuOCS.

3. In a gaseous discharge display/memory device comprising an ionizablegaseous medium in a sealed gas chamber formed by a pair of opposedcharge storage members backed by electrode members, the improvementwherein at least one charge storage member, consisting of at least onethin continuous dielectric film, has an effective thickness rangingbetween about 250 angstrom units and about'l50,000 angstrom units, the

minimum thickness beingsufflcient to store charges without deterioratingupon. gas discharge and the maximum thickness being less than thatthickness at which I the film becomes discontinuous due to breakdowncaused by deposition originated stresses, said thin dielectric filmcomprising a compound selected from MgF BeF CaF and NaCl. i

1. IN A GASEOUS DISCHARGE DISPLAY/MEMORY DEVICE COMPRISING AN IONIZABLEGASEOUS MEDIUM IN A SEALED GAS CHAMBER FORMED BY A PAIR OF OPPOSEDCHARGE STORAGE MEMBERS BAKED BY ELECTRODE MEMBERS THE IMPROVE, MENTWHEREIN AT LEACKED BY
 2. In a gaseous discharge display/memory devicecomprising an ionizable gaseous medium in a sealed gas chamber formed bya pair of opposed charge storage members backed by electrode members,the improvement wherein at least one charge storage member, comprising aplurality of layers, has an effective thickness ranging between about250 angstrom units and about 150,000 angstrom units, the minimumthickness being sufficient to store charges without deteriorating upongas discharge and the maximum thickness being less than that thicknessat which said charge storage member becomes discontinuous due tobreakdown caused by deposition originated stresses, the top layer ofsaid charge storage member comprising an electron emissive materialselected from Group IA elements, Group IA oxides, GaAs, GaP, InAs, InSb,InP, NiO, CsF, CsI, AgOCs and AuOCS.
 3. In a gaseous dischargedisplay/memory device comprising an ionizable gaseous medium in a sealedgas chamber formed by a pair of opposed charge storage members backed byelectrode members, the improvement wherein at least one charge storagemember, consisting of at least one thin continuous dielectric film, hasan effective thickness ranging between about 250 angstrom units andabout 150,000 angstrom units, the minimum thickness being sufficient tostore charges without deteriorating upon gas discharge and the maximumthickness being less than that thickness at which the film becomesdiscontinuous due to breakdown caused by deposition originated stresses,said thin dielectric film comprising a compound selected from MgF2,BeF2, CaF2 and NaCl.